N.M. Code R. § 20.3.4.422
A. When it is not practical to apply process or other engineering controls to control the concentrations of radioactive material in the air to values below those that define an airborne radioactivity area, the licensee or registrant shall, consistent with maintaining the total effective dose equivalent ALARA, increase monitoring and limit intakes by one or more of the following means:
[20.3.4.422 NMAC - Rp, 20.3.4.422 NMAC, 4/30/2009]